Hi there Ehsan and welcome to the Forum!
This is a request we’re tracking. Currently, you cannot separate these two permissions. If you can inspect, you can download. Although to open the downloaded document, you’ll need to have a Mac and Editor access to run Sketch.
A fellow Forum user just posted this in the Sugggest an idea category. Make sure to add your vote to that post. Our Product team keeps tracks of the most voted suggestions and the top ones are either already available in Sketch (like Smart Animate) or in development (Stack layout)
Here’s the post: Ability to control Download and Inspect permissions separately